Communications accessories, such as hands-free adapters, and the like, are typically deployed so as to act as an interface between a wireless communications device, such as a cellular telephone, and a vehicle's electrical system. Such accessories typically draw power from the vehicle's electrical system and supply power to the wireless communications device for charging, etc. When the vehicle is operating, the electrical load on the vehicle from the accessory and wireless communications device is relatively small compared to the overall electrical demands from the vehicle itself. However, when the vehicle is not operating, the accessory needs to consume as little power as possible so as to not drain the vehicle's battery. According to industrial standards for vehicles, the maximum allowed current consumption when the vehicle is not operating is typically one milliamp.
In the prior art, an ignition sense functionality had been developed which was used to determine whether the vehicle's ignition was on or off. Typically, this ignition sense functionality was accomplished by monitoring a switched power line of the vehicle. This ignition sense was then used to turn on or off the communications accessory in a binary fashion. That is, when the vehicle was on, the communications accessory would be on; but when the vehicle's ignition was off, the communications accessory would be powered off. Typically, a wireless communications device connected to the communications accessory had the same power on/off state as the communications accessory, meaning, for instance, that when the communications accessory was turned on, the wireless communications device was likewise turned on and when the accessory was turned off, the wireless communications device was turned off.
The user might, however, not always want the wireless communications device to power on when the vehicle ignition is turned on. For instance, if the user has physically powered the wireless communications device off, the user may not want to receive calls until the user intervenes to turn the wireless communications device on. However, under the prior art, the wireless communications device would be automatically powered on when the vehicle was turned on.
Further, it was possible that the installer of the ignition sense line might inadvertently connect the ignition sense to a line which was connected to continuous power (directly to the vehicle's battery). In such a situation, the accessory and wireless communications device will believe that the ignition is always on and will undesirably drain the vehicle's battery.
Still further, some communications accessories may have additional functionality, such as background noise adaptation capability, that should be ready for instant cooperation with the wireless communications device. That is, the communications accessory may have functions that take time to properly prepare for operation, but that should be essentially instantaneously ready for use when a wireless communications device is mated to the communications accessory, if the associated vehicle is turned on. Because such functions will most likely require the use of power, the ability of the communications accessory to properly determine the state of the vehicle's ignition will allow for more prudent power management associated with the operation of these functions.
Accordingly, there remains a need for a communications accessory that has a power management scheme wherein the power consumption of the communications accessory, both internally and through the communications accessory, is based not only on the state of the vehicle ignition, but also to the history of the wireless communications device attached to the communications accessory. Further, there is a separate need for a method for a communications accessory to determine whether the ignition sense line has been correctly installed.